Rhenium

This is quite a lot of rhenium, and it's not clear why anyone would make such a thick, heavy bar of it. Typical uses involve thin wires, fine powders, or chemical compounds, not half-inch-square solid bars.

Tungsten-rhenium alloy x-ray tube.
The conical disk in this sample is a heavy slab of tungsten-rhenium alloy. The structure above holds a filament that releases electrons, which are accelerated with a high voltage to strike the tungsten-rhenium disk, generating x-rays when they strike.
In operation the disk is spinning, because if it ever stopped the heat generated by the electrons slamming into the metal would start melting it. The small scratch towards the right is the explanation for why I have this tube: It's where the disk stopped and got burned.
Normally this whole setup would be inside a glass vacuum tube, but it broke in shipment, saving me the trouble.Source:eBay seller kentuckyspecialfxContributor:Theodore GrayAcquired:15 April, 2009Text Updated:15 April, 2009Price: $90Size: 4"Purity: 5%

Machined bar.
This absolutely stunning precision-machined bar of solid rhenium is worth a pretty serious amount of money, though Max got a great deal on it on eBay. Its density is around 20.5g/cc, slightly less than the theoretical density of 21.0g/cc. It's common for large bars of very high melting point metals like this to be lower in density than they should be, because they are formed by sintering a fine powder of the metal under high pressure (casting such a large piece being virtually impossible). The sintering process leaves microscopic voids, which must be compressed out by hammering, swaging, and the like in an attempt to beat the metal to the highest possible density.

I chose this sample to represent its element in my Photographic Periodic Table Poster. The sample photograph includes text exactly as it appears in the poster, which you are encouraged to buy a copy of.

Sintered button.
This is a compressed and sintered button of rhenium powder. It could be melted down into a solid button in an arc or e-beam furnace (see above), but it's interesting to keep a few of these around in pre-melted condition for comparison. I got this one from Oliver Sacks on a visit to New York, during which we visited a company in New Jersey to melt his kilogram of iridium down into a solid slab.Source:Oliver SacksContributor:Oliver SacksAcquired:4 August, 2004Price: DonatedSize: 0.75"Purity: 99.9%

Museum-grade sample.
In early 2004 Max Whitby and I started selling individual element samples identical or similar to the samples we use in the museum displays we build. These are top-quality samples presented in attractive forms appropriate to the particular element. They are for sale from Max's website and also on eBay where you will find an ever-changing selection of samples (click the link to see the current listings).
This bottle contains about 50 grams of arc-melted buttons made in Max's reduced-pressure argon-arc furnace.Source:Theodore GrayContributor:Theodore GrayAcquired:24 February, 2004Text Updated:11 August, 2007Price: See ListingSize: 2"Purity: >99%Sample Group:RGB Samples

Rhenium foil.
These are tiny little strips of rhenium foil about half an inch long. If they were made of aluminum this would be a pile of fluffy shreds. But it's rhenium, one of the hardest and densest elements, so instead it's a surprisingly heavy mass of fairly stiff strips.Source:eBay seller forsythiaContributor:Theodore GrayAcquired:29 September, 2003Price: $16Size: 0.5"Purity: 99.9%

Before and after arc-melting.
This shows what happens when you blast some compressed rhenium powder (left) with a high-current electric arc in an arc melting furnace (under an inert argon atmosphere): You get a nice shiny button of solid rhenium (right). Max Whitby made this button while visiting an arc melting furnace at Leeds university: It worked so well now he's working on building one himself, using a welder as the power source.

He'll use it to make solids out of powders for a number of elements that are much cheaper in powder form, for use as samples in his commercial element set.

Sample from the Everest Set.
Up until the early 1990's a company in Russia sold a periodic table collection with element samples. At some point their American distributor sold off the remaining stock to a man who is now selling them on eBay. The samples (except gases) weigh about 0.25 grams each, and the whole set comes in a very nice wooden box with a printed periodic table in the lid.

Sample from the RGB Set.
The Red Green and Blue company in England sells a very nice element collection in several versions. Max Whitby, the director of the company, very kindly donated a complete set to the periodic table table.

1cm wire.
A very small sample indeed, but since it's from David Franco, it is of course of the highest purity.Source:David FrancoContributor:Ed Pegg JrAcquired:16 August, 2002Price: $6Size: 0.4"Purity: 99.98%

Old photographic flash bulb.
Back in the dark ages, cameras used one-time-only flash bulbs that ignited a fine wire inside a glass bulb. We're not concerned here with the fine wire, but rather with the "igniter": these top-quality GE #5 bulbs were advertised as coming with "the guaranteed RHENIUM igniter". I don't know for sure what metal the wire in this one is made of, but I have a different type under zirconium which is labeled as using a wire of that metal (but that one doesn't say what it's igniter is made of).
Reports Tryggvi:

The woolly stuff in GE flashbulbs is zirconium. (I.e. , the stuff that burns and makes the light. The bulbs are also filled with a few atmospheres of oxygen). The flashbulbs in the cubes that were used on some Kodak Instamatics were not triggered electrically (with rhenium wire), but with a percussive pyrotechnic mix inside a little metallic tube that stuck out of the bulb.

Rhenium in Wolframite.
This is basically a fine powder which is said to have been determined by neutron activation analysis to be microscopic inclusions of rhenium in wolframite grains. No reason to doubt the claim. But it is a good bit of money to pay for a powder that, honestly, looks a lot like just about any other powder.
It is described as coming from eastern Transbaikal, Russia (interestingly the tag it came with is marked "E. Transbaikal, U.S.S.R.", indicating that the sample must have been collected some time ago).Source:Topaz Mineral ExplorationsContributor:Theodore GrayAcquired:20 July, 2002Price: $36Size: 0.001"Purity: >50%Sample Group:Powders

Big bag of beads. (External Sample)
This is a large ($18,000) order of platinum group metals placed by an excellent customer of my partner Max Whitby's element sales business. I happened to be visiting Max in London just before the order needed to be shipped to our customer in the US, so I hand-carried the precious cargo home rather than risking international shipping. These beads were made by Max in his reduced pressure argon arc furnace.

Big bag of beads. (External Sample)
This is part of a large ($18,000) order of platinum group metals placed by an excellent customer of my partner Max Whitby's element sales business. I happened to be visiting Max in London just before the order needed to be shipped to our customer in the US, so I hand-carried the precious cargo home rather than risking international shipping. These beads are made by Max in his reduced pressure argon arc furnace.

The order consisted of equal volumes of ruthenium, rhenium, osmium, and iridium. Here is what the whole collection looks like:

The customer wishes to remain anonymous, so you'll just have to keep wondering where this remarkable trove of rare metals currently resides: The only thing you can be sure of is that I don't have it.Location: AnonymousPhotographed:4 September, 2007Text Updated:6 September, 2007Size: 0.25"Purity: 99.99%